0-6748: Best Practice for Flexible Pavement Structure Widening Projects

Introduction

Project Purpose

• Objective: identify best practices for improving pavement performance on projects involving widening of narrow pavement structures

Reasons for Widening• Reasons:– Improve safety

• Edge failures & vehicle control• Greater traffic separation

– Enhance pavement performance• Edges deteriorating from softening due to

poor drainage• Reduce rutting due to tire loads at edges

Other Reasons?

• Narrow widening: adding 1 - 6 ft. width to shoulder

Construction Challenges

• Narrow work areas• Variable subgrade support• Surface and subsurface drainage• Potential need for acquisition of additional ROW• Keeping time short per task to maintain traffic flow• Narrow widening equipment not worth purchase• Project choices can depend on funding source

– CAT1, CAT8, RMC, In House

Failures

• Difference between old and new structure– Differences in thickness, material properties, and

compaction

– Can result in:• Rutting in existing or new pav’t• Uneven settlements• Cracking• Different load bearing capacities for both structures

(Varin & Saarenketo, 2012)

Failures• Joint construction and location– Should not be placed under/near wheel path– Traffic loading can cause reflection cracking

(Varin & Saarenketo, 2012)

Failures• Settlement– Sufficient compaction of new structure else,

differential settlement could occur

(Varin & Saarenketo, 2012)

Failures

• Moisture penetration

– Should:• Maintain lateral drainage within pavement structure • Proper Selection of base materials key• Good Construction Inspection

– Else, can cause:• Moisture penetration - base, subgrade softening• Swelling and heave of heavy clays

(Varin & Saarenketo, 2012)

Failures• Drainage– Maintain sufficient pavement surface drainage– Can result in:• decreased bearing capacity • Edge deformation• Ponding of water (accelerates deformation - safety)

(Varin & Saarenketo, 2012)

Failures• Slope stability– Should ensure stability of side slopes

(inner & outer)– Problems if ROW space is limited

– If steep inner slope:• Could result in poor compaction of

widened section– cause shear failure & edge

deformation– Structure widening a challenge

Workshop Webinar

• Webinar Purpose:– Obtain expert opinions– Experience in pavement widening projects• TxDOT personnel & transportation agencies• Industry representatives• Contractors• Construction equipment manufacturers

Workshop Webinar

• Contractors, construction equipment manufacturers & suppliers, & construction industry representatives– Identify construction projects performed well/not well– Good practices– Guidelines, specifications, standards– Equipment

• TxDOT Districts– Discuss projects that performed well/not well– Good practices– Guidelines, specifications, standards